Measuring a Strain’s Strength

When the plant is heated, it undergoes a process called decarboxylation, where THCA is converted to THC.

Lab testing of marijuana is now commonplace in areas where medical or recreational marijuana is permitted. Marijuana labs test for a number of things, including total cannabinoid content.

Labs test for THCA, and use a mathematical formula to determine the THC content. This is because the conversion from THCA to THC involves a loss of molecular mass, and strain potencies are measured as a percentage of the total weight.

But the figure produced from these mathematical conversions can often be misleading, explains Alec Dixon, co-founder of SC Laboratories, a large laboratory facility in Santa Cruz, California.

The equation uses a mass weight correction of 12 percent, which would only occur “in a perfect theoretical vacuum,” he says.

Labs have not developed a reliable, consistent method for testing for THC value, so THCA is the more accurate and routine way to discuss cannabis potency.

For this reason, Dixon says it’s the better figure to pay attention to while selecting a strain.

“Looking at the THCA value will give you the best idea of how much THC will be there when you use it,” says Dixon, “without the lab doing any math to see how much will convert, which could potentially be wrong.”

What Are The Most Potent Strains?

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The highest potency strains tend to have around 30% THCA.

Labs in places like Colorado and California — where recreational cannabis is now legal at the state level — are reporting average THCA levels around 20 percent.

Most of the cannabis tested by Colorado’s largest network of testing labs, AgriScience Labs, tests “in the twenty-something range” for THCA, says Sales and Marketing Director Hayley Witherell.

Dixon, with SC Laboratories, says his company sees 15 to 25 percent THCA on average.

Because of a mounting interest over the decades in the strength of cannabis — and growers’ selective breeding to meet that demand — strains have risen in THCA, with many now topping 30 percent. These are considered the highest available varieties.

While some strains are known to be stronger overall, seeking out a strain by name alone does not guarantee certain potency. There can be quite a bit of variability within a strain depending on how it was grown.

For example, Banana OG (aka Chiquita Banana or Golden State Banana) is a popular and potent strain in Northern California that typically tests between 26 to 28 percent, says Dixon, but “whenever it’s grown immaculately — perfectly — there can be 33 or 34 percent THCA in that strain.”

Has Marijuana Gotten Stronger Over Time?

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The marijuana previous generations consumed was significantly less powerful. As recently as the 1990s, the average THC content was around 4 percent, according to a study by the National Institutes of Health.

Dixon believes that the advent of lab testing contributed to the fixation with high THC content. He believes there is a false impression that testing high in THC means a strain is the strongest or the best, and that’s “a slippery slope”, he says.

However, Dixon says the trend is changing once again. As we come to understand the cannabis plant better — for instance, the role of terpenes and the entourage effect — consumers and growers are increasingly interested in more balanced strains.

“Virtually everything we test is all really high in THC and really low in every other compound, because THC is what’s been bred for over the last 30 years,” Dixon says.

“But now that people are finding out about these other cannabinoids, like CBD and THCV, people are starting to breed them back into different strains, and you’ll see them now in different ratios.”

Ryan Randolph, director of AgriScience Labs’ Western Slope Lab, reports a similar observation. While innovative growers continue to push the envelope to get stronger strains, there is a limit to how much THCA a plant can offer, he explains.

“You can’t grow bud that is 100-percent THCA because you also need to have other biomass required to support life, such as proteins, fat, sugars, etc.,” says Randolph.

“While we do not know exactly what that limit is, we can say that the highest THC levels we have seen are in the low 30-percent range.”

Why THC Can Be Misleading

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Solely looking at THC content won’t guarantee the best, or even the strongest, experience. Terpenes, which are responsible for flavor and aroma, are crucial to the quality and experience of a strain, so they should also be considered.

A strain that is balanced in its cannabinoid and terpene profiles offers a richer experience because these compounds work better together than alone. This is known as the entourage effect.

“It’s the symphony of those different compounds working together that brings about the really unique and enjoyable effects of cannabis,” says Dixon.

A strain that is bred for potency and grown perfectly could be harvested, dried and cured improperly or poorly, resulting in miniscule terpene content — which means the high THCA content could be really misleading.

“Terpene content will give you a lot more information about the characteristics of the plant, how well it was grown and cured, and what you can come to expect from the effects,” says Dixon.

Terpenes can determine whether your bud is sedating or stimulating, for instance.